Shen Yingjie

A Graphene-Based Passively Q-Switched Ho:YAG Laser

A 2.09-μm in-band pumped passively Q-switched Ho:YAG laser is demonstrated. Single layer graphene deposited on a quartz substrate is used as the saturable absorber for the Q-switched operation. The minimum pulse width of 2.11 μs is obtained at an average output power of 100 mW, corresponding to a pulse repetition frequency of 57.1 kHz and the pulse energy of 1.75 μJ. The beam quality factors M2 of the Q-switched laser are 1.18 and 1.22 in the horizontal and longitudinal direction, respectively. The optical-to-optical conversion efficiency of the passively Q-switched laser is 4.3%, which is the highest conversion efficiency in the 2 μm wavelength, to the best of our knowledge. It shows clearly that the Ho:YAG crystal is a potential gain medium in the 2 μm range for the graphene application.

High Power Q-Switched Dual-End-Pumped Ho:YAG Laser

We report the high power acousto-optically Q-switched operation of a dual-end-pumped Ho:YAG laser at room temperature. For the Q-swithched mode, a maximum pulse energy of 2.4 mJ and a minimum pulse width of 23 ns at the repetition rate of 10 kHz are achieved, resulting in a peak power of 104.3 kW. The beam quality factor of M2 ~ 1.5, which is demonstrated by a knife-edge method. In addition, the Ho:YAG laser is employed as a pumping source of ZGP optical parametric oscillator, and its total average output power is 13.2 W at 3.9 μm and 4.4 μm with a slope efficiency of 68.4%.

A Mid-IR Optical Parametric Oscillator Pumped by an Actively Q-Switched Ho:YAG Ceramic Laser

We demonstrate a mid-IR ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumped by a dual-end-pumped actively acousto-optic Q-switched Ho:YAG ceramic laser. The maximum average output power of 35 W is obtained at a pulse repetition frequency of 20kHz from the Ho:YAG ceramic laser. Under the maximum incident pump power of Ho:YAG ceramic laser, the maximum output power of 14 W is obtained from the ZGP OPO, corresponding to the slope efficiency of 49.6% with respect to the incident pump power. The wavelength can be tuned from 3.5 μm to 4.2 μm (signal), corresponding to 5.2–4.1 μm (idler). The beam quality M2 is less than 2.3 from the ZGP OPO.

In-Band Pumped High Power Ho:YAG Ceramic Laser by a Tm:YLF Laser

We demonstrate a high power Ho:YAG ceramic laser resonantly pumped by a Tm:YLF laser at 1908 nm. The lasing characteristics of a 1.0 at.% Ho3+-doped YAG ceramic are investigated and compared with different output couplers. By using an output coupler of 50% transmission and 100 mm radius of curvature, a 26.8 W continuous wave is obtained at 2091 nm, corresponding to a slope efficiency of 57.9% and an optical to optical efficiency of 55.8% with respect to the absorbed pump power.

Performance of a c − and a -Cut Ho:YAP Laser at Room Temperature

Continuous-wave operation of room-temperature c- and a-cut Ho:YAP lasers resonantly end-pumped by a diode-pumped Tm:YLF laser at 1.91 μm are comparatively investigated. The maximum output powers of 7.8 W at 2103 nm and 6.09 W at 2130 nm for c-cut Ho:YAP crystal are obtained. The maximum output power of 8.78 W at 2119 nm for a-cut Ho:YAlO3 crystal is achieved. The maximum slope efficiency in terms of absorbed pump power approximately reaches 57.8% for c-oriented crystal and about 52.7% for a-oriented crystal.